Commit | Line | Data |
---|---|---|
71bfa161 JA |
1 | Table of contents |
2 | ----------------- | |
3 | ||
4 | 1. Overview | |
5 | 2. How fio works | |
6 | 3. Running fio | |
7 | 4. Job file format | |
8 | 5. Detailed list of parameters | |
9 | 6. Normal output | |
10 | 7. Terse output | |
11 | ||
12 | ||
13 | 1.0 Overview and history | |
14 | ------------------------ | |
15 | fio was originally written to save me the hassle of writing special test | |
16 | case programs when I wanted to test a specific workload, either for | |
17 | performance reasons or to find/reproduce a bug. The process of writing | |
18 | such a test app can be tiresome, especially if you have to do it often. | |
19 | Hence I needed a tool that would be able to simulate a given io workload | |
20 | without resorting to writing a tailored test case again and again. | |
21 | ||
22 | A test work load is difficult to define, though. There can be any number | |
23 | of processes or threads involved, and they can each be using their own | |
24 | way of generating io. You could have someone dirtying large amounts of | |
25 | memory in an memory mapped file, or maybe several threads issuing | |
26 | reads using asynchronous io. fio needed to be flexible enough to | |
27 | simulate both of these cases, and many more. | |
28 | ||
29 | 2.0 How fio works | |
30 | ----------------- | |
31 | The first step in getting fio to simulate a desired io workload, is | |
32 | writing a job file describing that specific setup. A job file may contain | |
33 | any number of threads and/or files - the typical contents of the job file | |
34 | is a global section defining shared parameters, and one or more job | |
35 | sections describing the jobs involved. When run, fio parses this file | |
36 | and sets everything up as described. If we break down a job from top to | |
37 | bottom, it contains the following basic parameters: | |
38 | ||
39 | IO type Defines the io pattern issued to the file(s). | |
40 | We may only be reading sequentially from this | |
41 | file(s), or we may be writing randomly. Or even | |
42 | mixing reads and writes, sequentially or randomly. | |
43 | ||
44 | Block size In how large chunks are we issuing io? This may be | |
45 | a single value, or it may describe a range of | |
46 | block sizes. | |
47 | ||
48 | IO size How much data are we going to be reading/writing. | |
49 | ||
50 | IO engine How do we issue io? We could be memory mapping the | |
51 | file, we could be using regular read/write, we | |
d0ff85df | 52 | could be using splice, async io, syslet, or even |
71bfa161 JA |
53 | SG (SCSI generic sg). |
54 | ||
6c219763 | 55 | IO depth If the io engine is async, how large a queuing |
71bfa161 JA |
56 | depth do we want to maintain? |
57 | ||
58 | IO type Should we be doing buffered io, or direct/raw io? | |
59 | ||
60 | Num files How many files are we spreading the workload over. | |
61 | ||
62 | Num threads How many threads or processes should we spread | |
63 | this workload over. | |
64 | ||
65 | The above are the basic parameters defined for a workload, in addition | |
66 | there's a multitude of parameters that modify other aspects of how this | |
67 | job behaves. | |
68 | ||
69 | ||
70 | 3.0 Running fio | |
71 | --------------- | |
72 | See the README file for command line parameters, there are only a few | |
73 | of them. | |
74 | ||
75 | Running fio is normally the easiest part - you just give it the job file | |
76 | (or job files) as parameters: | |
77 | ||
78 | $ fio job_file | |
79 | ||
80 | and it will start doing what the job_file tells it to do. You can give | |
81 | more than one job file on the command line, fio will serialize the running | |
82 | of those files. Internally that is the same as using the 'stonewall' | |
83 | parameter described the the parameter section. | |
84 | ||
b4692828 JA |
85 | If the job file contains only one job, you may as well just give the |
86 | parameters on the command line. The command line parameters are identical | |
87 | to the job parameters, with a few extra that control global parameters | |
88 | (see README). For example, for the job file parameter iodepth=2, the | |
c2b1e753 JA |
89 | mirror command line option would be --iodepth 2 or --iodepth=2. You can |
90 | also use the command line for giving more than one job entry. For each | |
91 | --name option that fio sees, it will start a new job with that name. | |
92 | Command line entries following a --name entry will apply to that job, | |
93 | until there are no more entries or a new --name entry is seen. This is | |
94 | similar to the job file options, where each option applies to the current | |
95 | job until a new [] job entry is seen. | |
b4692828 | 96 | |
71bfa161 JA |
97 | fio does not need to run as root, except if the files or devices specified |
98 | in the job section requires that. Some other options may also be restricted, | |
6c219763 | 99 | such as memory locking, io scheduler switching, and decreasing the nice value. |
71bfa161 JA |
100 | |
101 | ||
102 | 4.0 Job file format | |
103 | ------------------- | |
104 | As previously described, fio accepts one or more job files describing | |
105 | what it is supposed to do. The job file format is the classic ini file, | |
106 | where the names enclosed in [] brackets define the job name. You are free | |
107 | to use any ascii name you want, except 'global' which has special meaning. | |
108 | A global section sets defaults for the jobs described in that file. A job | |
109 | may override a global section parameter, and a job file may even have | |
110 | several global sections if so desired. A job is only affected by a global | |
65db0851 JA |
111 | section residing above it. If the first character in a line is a ';' or a |
112 | '#', the entire line is discarded as a comment. | |
71bfa161 JA |
113 | |
114 | So lets look at a really simple job file that define to threads, each | |
115 | randomly reading from a 128MiB file. | |
116 | ||
117 | ; -- start job file -- | |
118 | [global] | |
119 | rw=randread | |
120 | size=128m | |
121 | ||
122 | [job1] | |
123 | ||
124 | [job2] | |
125 | ||
126 | ; -- end job file -- | |
127 | ||
128 | As you can see, the job file sections themselves are empty as all the | |
129 | described parameters are shared. As no filename= option is given, fio | |
c2b1e753 JA |
130 | makes up a filename for each of the jobs as it sees fit. On the command |
131 | line, this job would look as follows: | |
132 | ||
133 | $ fio --name=global --rw=randread --size=128m --name=job1 --name=job2 | |
134 | ||
71bfa161 JA |
135 | |
136 | Lets look at an example that have a number of processes writing randomly | |
137 | to files. | |
138 | ||
139 | ; -- start job file -- | |
140 | [random-writers] | |
141 | ioengine=libaio | |
142 | iodepth=4 | |
143 | rw=randwrite | |
144 | bs=32k | |
145 | direct=0 | |
146 | size=64m | |
147 | numjobs=4 | |
148 | ||
149 | ; -- end job file -- | |
150 | ||
151 | Here we have no global section, as we only have one job defined anyway. | |
152 | We want to use async io here, with a depth of 4 for each file. We also | |
153 | increased the buffer size used to 32KiB and define numjobs to 4 to | |
154 | fork 4 identical jobs. The result is 4 processes each randomly writing | |
b4692828 JA |
155 | to their own 64MiB file. Instead of using the above job file, you could |
156 | have given the parameters on the command line. For this case, you would | |
157 | specify: | |
158 | ||
159 | $ fio --name=random-writers --ioengine=libaio --iodepth=4 --rw=randwrite --bs=32k --direct=0 --size=64m --numjobs=4 | |
71bfa161 JA |
160 | |
161 | fio ships with a few example job files, you can also look there for | |
162 | inspiration. | |
163 | ||
164 | ||
165 | 5.0 Detailed list of parameters | |
166 | ------------------------------- | |
167 | ||
168 | This section describes in details each parameter associated with a job. | |
169 | Some parameters take an option of a given type, such as an integer or | |
170 | a string. The following types are used: | |
171 | ||
172 | str String. This is a sequence of alpha characters. | |
173 | int Integer. A whole number value, may be negative. | |
174 | siint SI integer. A whole number value, which may contain a postfix | |
175 | describing the base of the number. Accepted postfixes are k/m/g, | |
6c219763 | 176 | meaning kilo, mega, and giga. So if you want to specify 4096, |
71bfa161 JA |
177 | you could either write out '4096' or just give 4k. The postfixes |
178 | signify base 2 values, so 1024 is 1k and 1024k is 1m and so on. | |
179 | bool Boolean. Usually parsed as an integer, however only defined for | |
180 | true and false (1 and 0). | |
181 | irange Integer range with postfix. Allows value range to be given, such | |
0c9baf91 JA |
182 | as 1024-4096. A colon may also be used as the seperator, eg |
183 | 1k:4k. If the option allows two sets of ranges, they can be | |
184 | specified with a ',' or '/' delimiter: 1k-4k/8k-32k. Also see | |
185 | siint. | |
71bfa161 JA |
186 | |
187 | With the above in mind, here follows the complete list of fio job | |
188 | parameters. | |
189 | ||
190 | name=str ASCII name of the job. This may be used to override the | |
191 | name printed by fio for this job. Otherwise the job | |
c2b1e753 | 192 | name is used. On the command line this parameter has the |
6c219763 | 193 | special purpose of also signaling the start of a new |
c2b1e753 | 194 | job. |
71bfa161 | 195 | |
61697c37 JA |
196 | description=str Text description of the job. Doesn't do anything except |
197 | dump this text description when this job is run. It's | |
198 | not parsed. | |
199 | ||
71bfa161 JA |
200 | directory=str Prefix filenames with this directory. Used to places files |
201 | in a different location than "./". | |
202 | ||
203 | filename=str Fio normally makes up a filename based on the job name, | |
204 | thread number, and file number. If you want to share | |
205 | files between threads in a job or several jobs, specify | |
ed92ac0c JA |
206 | a filename for each of them to override the default. If |
207 | the ioengine used is 'net', the filename is the host and | |
208 | port to connect to in the format of =host:port. | |
71bfa161 JA |
209 | |
210 | rw=str Type of io pattern. Accepted values are: | |
211 | ||
212 | read Sequential reads | |
213 | write Sequential writes | |
214 | randwrite Random writes | |
215 | randread Random reads | |
216 | rw Sequential mixed reads and writes | |
217 | randrw Random mixed reads and writes | |
218 | ||
219 | For the mixed io types, the default is to split them 50/50. | |
220 | For certain types of io the result may still be skewed a bit, | |
221 | since the speed may be different. | |
222 | ||
ee738499 JA |
223 | randrepeat=bool For random IO workloads, seed the generator in a predictable |
224 | way so that results are repeatable across repetitions. | |
225 | ||
71bfa161 JA |
226 | size=siint The total size of file io for this job. This may describe |
227 | the size of the single file the job uses, or it may be | |
228 | divided between the number of files in the job. If the | |
229 | file already exists, the file size will be adjusted to this | |
230 | size if larger than the current file size. If this parameter | |
231 | is not given and the file exists, the file size will be used. | |
232 | ||
f90eff5a JA |
233 | bs=siint The block size used for the io units. Defaults to 4k. Values |
234 | can be given for both read and writes. If a single siint is | |
235 | given, it will apply to both. If a second siint is specified | |
236 | after a comma, it will apply to writes only. In other words, | |
237 | the format is either bs=read_and_write or bs=read,write. | |
238 | bs=4k,8k will thus use 4k blocks for reads, and 8k blocks | |
787f7e95 JA |
239 | for writes. If you only wish to set the write size, you |
240 | can do so by passing an empty read size - bs=,8k will set | |
241 | 8k for writes and leave the read default value. | |
a00735e6 | 242 | |
71bfa161 JA |
243 | bsrange=irange Instead of giving a single block size, specify a range |
244 | and fio will mix the issued io block sizes. The issued | |
245 | io unit will always be a multiple of the minimum value | |
f90eff5a JA |
246 | given (also see bs_unaligned). Applies to both reads and |
247 | writes, however a second range can be given after a comma. | |
248 | See bs=. | |
a00735e6 | 249 | |
690adba3 JA |
250 | bs_unaligned If this option is given, any byte size value within bsrange |
251 | may be used as a block range. This typically wont work with | |
252 | direct IO, as that normally requires sector alignment. | |
71bfa161 JA |
253 | |
254 | nrfiles=int Number of files to use for this job. Defaults to 1. | |
255 | ||
256 | ioengine=str Defines how the job issues io to the file. The following | |
257 | types are defined: | |
258 | ||
259 | sync Basic read(2) or write(2) io. lseek(2) is | |
260 | used to position the io location. | |
261 | ||
262 | libaio Linux native asynchronous io. | |
263 | ||
264 | posixaio glibc posix asynchronous io. | |
265 | ||
266 | mmap File is memory mapped and data copied | |
267 | to/from using memcpy(3). | |
268 | ||
269 | splice splice(2) is used to transfer the data and | |
270 | vmsplice(2) to transfer data from user | |
271 | space to the kernel. | |
272 | ||
d0ff85df JA |
273 | syslet-rw Use the syslet system calls to make |
274 | regular read/write async. | |
275 | ||
71bfa161 | 276 | sg SCSI generic sg v3 io. May either be |
6c219763 | 277 | synchronous using the SG_IO ioctl, or if |
71bfa161 JA |
278 | the target is an sg character device |
279 | we use read(2) and write(2) for asynchronous | |
280 | io. | |
281 | ||
a94ea28b JA |
282 | null Doesn't transfer any data, just pretends |
283 | to. This is mainly used to exercise fio | |
284 | itself and for debugging/testing purposes. | |
285 | ||
ed92ac0c JA |
286 | net Transfer over the network to given host:port. |
287 | 'filename' must be set appropriately to | |
288 | filename=host:port regardless of send | |
289 | or receive, if the latter only the port | |
290 | argument is used. | |
291 | ||
71bfa161 JA |
292 | iodepth=int This defines how many io units to keep in flight against |
293 | the file. The default is 1 for each file defined in this | |
294 | job, can be overridden with a larger value for higher | |
295 | concurrency. | |
296 | ||
e916b390 JA |
297 | iodepth_low=int The low water mark indicating when to start filling |
298 | the queue again. Defaults to the same as iodepth, meaning | |
299 | that fio will attempt to keep the queue full at all times. | |
300 | If iodepth is set to eg 16 and iodepth_low is set to 4, then | |
301 | after fio has filled the queue of 16 requests, it will let | |
302 | the depth drain down to 4 before starting to fill it again. | |
303 | ||
71bfa161 | 304 | direct=bool If value is true, use non-buffered io. This is usually |
76a43db4 JA |
305 | O_DIRECT. |
306 | ||
307 | buffered=bool If value is true, use buffered io. This is the opposite | |
308 | of the 'direct' option. Defaults to true. | |
71bfa161 JA |
309 | |
310 | offset=siint Start io at the given offset in the file. The data before | |
311 | the given offset will not be touched. This effectively | |
312 | caps the file size at real_size - offset. | |
313 | ||
314 | fsync=int If writing to a file, issue a sync of the dirty data | |
315 | for every number of blocks given. For example, if you give | |
316 | 32 as a parameter, fio will sync the file for every 32 | |
317 | writes issued. If fio is using non-buffered io, we may | |
318 | not sync the file. The exception is the sg io engine, which | |
6c219763 | 319 | synchronizes the disk cache anyway. |
71bfa161 JA |
320 | |
321 | overwrite=bool If writing to a file, setup the file first and do overwrites. | |
322 | ||
323 | end_fsync=bool If true, fsync file contents when the job exits. | |
324 | ||
6c219763 | 325 | rwmixcycle=int Value in milliseconds describing how often to switch between |
71bfa161 JA |
326 | reads and writes for a mixed workload. The default is |
327 | 500 msecs. | |
328 | ||
329 | rwmixread=int How large a percentage of the mix should be reads. | |
330 | ||
331 | rwmixwrite=int How large a percentage of the mix should be writes. If both | |
332 | rwmixread and rwmixwrite is given and the values do not add | |
333 | up to 100%, the latter of the two will be used to override | |
334 | the first. | |
335 | ||
bb8895e0 JA |
336 | norandommap Normally fio will cover every block of the file when doing |
337 | random IO. If this option is given, fio will just get a | |
338 | new random offset without looking at past io history. This | |
339 | means that some blocks may not be read or written, and that | |
340 | some blocks may be read/written more than once. This option | |
341 | is mutually exclusive with verify= for that reason. | |
342 | ||
71bfa161 JA |
343 | nice=int Run the job with the given nice value. See man nice(2). |
344 | ||
345 | prio=int Set the io priority value of this job. Linux limits us to | |
346 | a positive value between 0 and 7, with 0 being the highest. | |
347 | See man ionice(1). | |
348 | ||
349 | prioclass=int Set the io priority class. See man ionice(1). | |
350 | ||
351 | thinktime=int Stall the job x microseconds after an io has completed before | |
352 | issuing the next. May be used to simulate processing being | |
48097d5c JA |
353 | done by an application. See thinktime_blocks and |
354 | thinktime_spin. | |
355 | ||
356 | thinktime_spin=int | |
357 | Only valid if thinktime is set - pretend to spend CPU time | |
358 | doing something with the data received, before falling back | |
359 | to sleeping for the rest of the period specified by | |
360 | thinktime. | |
9c1f7434 JA |
361 | |
362 | thinktime_blocks | |
363 | Only valid if thinktime is set - control how many blocks | |
364 | to issue, before waiting 'thinktime' usecs. If not set, | |
365 | defaults to 1 which will make fio wait 'thinktime' usecs | |
366 | after every block. | |
71bfa161 JA |
367 | |
368 | rate=int Cap the bandwidth used by this job to this number of KiB/sec. | |
369 | ||
370 | ratemin=int Tell fio to do whatever it can to maintain at least this | |
371 | bandwidth. | |
372 | ||
373 | ratecycle=int Average bandwidth for 'rate' and 'ratemin' over this number | |
6c219763 | 374 | of milliseconds. |
71bfa161 JA |
375 | |
376 | cpumask=int Set the CPU affinity of this job. The parameter given is a | |
377 | bitmask of allowed CPU's the job may run on. See man | |
378 | sched_setaffinity(2). | |
379 | ||
380 | startdelay=int Start this job the specified number of seconds after fio | |
381 | has started. Only useful if the job file contains several | |
382 | jobs, and you want to delay starting some jobs to a certain | |
383 | time. | |
384 | ||
03b74b3e | 385 | runtime=int Tell fio to terminate processing after the specified number |
71bfa161 JA |
386 | of seconds. It can be quite hard to determine for how long |
387 | a specified job will run, so this parameter is handy to | |
388 | cap the total runtime to a given time. | |
389 | ||
390 | invalidate=bool Invalidate the buffer/page cache parts for this file prior | |
391 | to starting io. Defaults to true. | |
392 | ||
393 | sync=bool Use sync io for buffered writes. For the majority of the | |
394 | io engines, this means using O_SYNC. | |
395 | ||
396 | mem=str Fio can use various types of memory as the io unit buffer. | |
397 | The allowed values are: | |
398 | ||
399 | malloc Use memory from malloc(3) as the buffers. | |
400 | ||
401 | shm Use shared memory as the buffers. Allocated | |
402 | through shmget(2). | |
403 | ||
74b025b0 JA |
404 | shmhuge Same as shm, but use huge pages as backing. |
405 | ||
313cb206 JA |
406 | mmap Use mmap to allocate buffers. May either be |
407 | anonymous memory, or can be file backed if | |
408 | a filename is given after the option. The | |
409 | format is mem=mmap:/path/to/file. | |
71bfa161 | 410 | |
d0bdaf49 JA |
411 | mmaphuge Use a memory mapped huge file as the buffer |
412 | backing. Append filename after mmaphuge, ala | |
413 | mem=mmaphuge:/hugetlbfs/file | |
414 | ||
71bfa161 | 415 | The area allocated is a function of the maximum allowed |
5394ae5f JA |
416 | bs size for the job, multiplied by the io depth given. Note |
417 | that for shmhuge and mmaphuge to work, the system must have | |
418 | free huge pages allocated. This can normally be checked | |
419 | and set by reading/writing /proc/sys/vm/nr_hugepages on a | |
420 | Linux system. Fio assumes a huge page is 4MiB in size. So | |
421 | to calculate the number of huge pages you need for a given | |
422 | job file, add up the io depth of all jobs (normally one unless | |
423 | iodepth= is used) and multiply by the maximum bs set. Then | |
424 | divide that number by the huge page size. You can see the | |
425 | size of the huge pages in /proc/meminfo. If no huge pages | |
426 | are allocated by having a non-zero number in nr_hugepages, | |
56bb17f2 | 427 | using mmaphuge or shmhuge will fail. Also see hugepage-size. |
5394ae5f JA |
428 | |
429 | mmaphuge also needs to have hugetlbfs mounted and the file | |
430 | location should point there. So if it's mounted in /huge, | |
431 | you would use mem=mmaphuge:/huge/somefile. | |
71bfa161 | 432 | |
56bb17f2 JA |
433 | hugepage-size=siint |
434 | Defines the size of a huge page. Must at least be equal | |
435 | to the system setting, see /proc/meminfo. Defaults to 4MiB. | |
c51074e7 JA |
436 | Should probably always be a multiple of megabytes, so using |
437 | hugepage-size=Xm is the preferred way to set this to avoid | |
438 | setting a non-pow-2 bad value. | |
56bb17f2 | 439 | |
71bfa161 JA |
440 | exitall When one job finishes, terminate the rest. The default is |
441 | to wait for each job to finish, sometimes that is not the | |
442 | desired action. | |
443 | ||
444 | bwavgtime=int Average the calculated bandwidth over the given time. Value | |
6c219763 | 445 | is specified in milliseconds. |
71bfa161 JA |
446 | |
447 | create_serialize=bool If true, serialize the file creating for the jobs. | |
448 | This may be handy to avoid interleaving of data | |
449 | files, which may greatly depend on the filesystem | |
450 | used and even the number of processors in the system. | |
451 | ||
452 | create_fsync=bool fsync the data file after creation. This is the | |
453 | default. | |
454 | ||
e545a6ce JA |
455 | unlink=bool Unlink the job files when done. Not the default, as repeated |
456 | runs of that job would then waste time recreating the fileset | |
457 | again and again. | |
71bfa161 JA |
458 | |
459 | loops=int Run the specified number of iterations of this job. Used | |
460 | to repeat the same workload a given number of times. Defaults | |
461 | to 1. | |
462 | ||
463 | verify=str If writing to a file, fio can verify the file contents | |
464 | after each iteration of the job. The allowed values are: | |
465 | ||
466 | md5 Use an md5 sum of the data area and store | |
467 | it in the header of each block. | |
468 | ||
469 | crc32 Use a crc32 sum of the data area and store | |
470 | it in the header of each block. | |
471 | ||
6c219763 | 472 | This option can be used for repeated burn-in tests of a |
71bfa161 JA |
473 | system to make sure that the written data is also |
474 | correctly read back. | |
475 | ||
476 | stonewall Wait for preceeding jobs in the job file to exit, before | |
477 | starting this one. Can be used to insert serialization | |
478 | points in the job file. | |
479 | ||
480 | numjobs=int Create the specified number of clones of this job. May be | |
481 | used to setup a larger number of threads/processes doing | |
482 | the same thing. | |
483 | ||
484 | thread fio defaults to forking jobs, however if this option is | |
485 | given, fio will use pthread_create(3) to create threads | |
486 | instead. | |
487 | ||
488 | zonesize=siint Divide a file into zones of the specified size. See zoneskip. | |
489 | ||
490 | zoneskip=siint Skip the specified number of bytes when zonesize data has | |
491 | been read. The two zone options can be used to only do | |
492 | io on zones of a file. | |
493 | ||
076efc7c JA |
494 | write_iolog=str Write the issued io patterns to the specified file. See |
495 | read_iolog. | |
71bfa161 | 496 | |
076efc7c | 497 | read_iolog=str Open an iolog with the specified file name and replay the |
71bfa161 JA |
498 | io patterns it contains. This can be used to store a |
499 | workload and replay it sometime later. | |
500 | ||
501 | write_bw_log If given, write a bandwidth log of the jobs in this job | |
502 | file. Can be used to store data of the bandwidth of the | |
e0da9bc2 JA |
503 | jobs in their lifetime. The included fio_generate_plots |
504 | script uses gnuplot to turn these text files into nice | |
505 | graphs. | |
71bfa161 JA |
506 | |
507 | write_lat_log Same as write_bw_log, except that this option stores io | |
508 | completion latencies instead. | |
509 | ||
510 | lockmem=siint Pin down the specified amount of memory with mlock(2). Can | |
511 | potentially be used instead of removing memory or booting | |
512 | with less memory to simulate a smaller amount of memory. | |
513 | ||
514 | exec_prerun=str Before running this job, issue the command specified | |
515 | through system(3). | |
516 | ||
517 | exec_postrun=str After the job completes, issue the command specified | |
518 | though system(3). | |
519 | ||
520 | ioscheduler=str Attempt to switch the device hosting the file to the specified | |
521 | io scheduler before running. | |
522 | ||
523 | cpuload=int If the job is a CPU cycle eater, attempt to use the specified | |
524 | percentage of CPU cycles. | |
525 | ||
526 | cpuchunks=int If the job is a CPU cycle eater, split the load into | |
6c219763 | 527 | cycles of the given time. In milliseconds. |
71bfa161 JA |
528 | |
529 | ||
530 | 6.0 Interpreting the output | |
531 | --------------------------- | |
532 | ||
533 | fio spits out a lot of output. While running, fio will display the | |
534 | status of the jobs created. An example of that would be: | |
535 | ||
73c8b082 | 536 | Threads: 1: [_r] [24.8% done] [ 13509/ 8334 kb/s] [eta 00h:01m:31s] |
71bfa161 JA |
537 | |
538 | The characters inside the square brackets denote the current status of | |
539 | each thread. The possible values (in typical life cycle order) are: | |
540 | ||
541 | Idle Run | |
542 | ---- --- | |
543 | P Thread setup, but not started. | |
544 | C Thread created. | |
545 | I Thread initialized, waiting. | |
546 | R Running, doing sequential reads. | |
547 | r Running, doing random reads. | |
548 | W Running, doing sequential writes. | |
549 | w Running, doing random writes. | |
550 | M Running, doing mixed sequential reads/writes. | |
551 | m Running, doing mixed random reads/writes. | |
552 | F Running, currently waiting for fsync() | |
553 | V Running, doing verification of written data. | |
554 | E Thread exited, not reaped by main thread yet. | |
555 | _ Thread reaped. | |
556 | ||
557 | The other values are fairly self explanatory - number of threads | |
6043c579 JA |
558 | currently running and doing io, rate of io since last check, and the estimated |
559 | completion percentage and time for the running group. It's impossible to | |
560 | estimate runtime of the following groups (if any). | |
71bfa161 JA |
561 | |
562 | When fio is done (or interrupted by ctrl-c), it will show the data for | |
563 | each thread, group of threads, and disks in that order. For each data | |
564 | direction, the output looks like: | |
565 | ||
566 | Client1 (g=0): err= 0: | |
567 | write: io= 32MiB, bw= 666KiB/s, runt= 50320msec | |
6104ddb6 JA |
568 | slat (msec): min= 0, max= 136, avg= 0.03, stdev= 1.92 |
569 | clat (msec): min= 0, max= 631, avg=48.50, stdev=86.82 | |
570 | bw (KiB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, stdev=681.68 | |
71bfa161 | 571 | cpu : usr=1.49%, sys=0.25%, ctx=7969 |
71619dc2 | 572 | IO depths : 1=0.1%, 2=0.3%, 4=0.5%, 8=99.0%, 16=0.0%, 32=0.0%, >32=0.0% |
ec118304 JA |
573 | lat (msec): 2=1.6%, 4=0.0%, 8=3.2%, 16=12.8%, 32=38.4%, 64=24.8%, 128=15.2% |
574 | lat (msec): 256=4.0%, 512=0.0%, 1024=0.0%, >=2048=0.0% | |
71bfa161 JA |
575 | |
576 | The client number is printed, along with the group id and error of that | |
577 | thread. Below is the io statistics, here for writes. In the order listed, | |
578 | they denote: | |
579 | ||
580 | io= Number of megabytes io performed | |
581 | bw= Average bandwidth rate | |
582 | runt= The runtime of that thread | |
583 | slat= Submission latency (avg being the average, dev being the | |
584 | standard deviation). This is the time it took to submit | |
585 | the io. For sync io, the slat is really the completion | |
586 | latency, since queue/complete is one operation there. | |
587 | clat= Completion latency. Same names as slat, this denotes the | |
588 | time from submission to completion of the io pieces. For | |
589 | sync io, clat will usually be equal (or very close) to 0, | |
590 | as the time from submit to complete is basically just | |
591 | CPU time (io has already been done, see slat explanation). | |
592 | bw= Bandwidth. Same names as the xlat stats, but also includes | |
593 | an approximate percentage of total aggregate bandwidth | |
594 | this thread received in this group. This last value is | |
595 | only really useful if the threads in this group are on the | |
596 | same disk, since they are then competing for disk access. | |
597 | cpu= CPU usage. User and system time, along with the number | |
598 | of context switches this thread went through. | |
71619dc2 JA |
599 | IO depths= The distribution of io depths over the job life time. The |
600 | numbers are divided into powers of 2, so for example the | |
601 | 16= entries includes depths up to that value but higher | |
602 | than the previous entry. In other words, it covers the | |
603 | range from 16 to 31. | |
ec118304 JA |
604 | IO latencies= The distribution of IO completion latencies. This is the |
605 | time from when IO leaves fio and when it gets completed. | |
606 | The numbers follow the same pattern as the IO depths, | |
607 | meaning that 2=1.6% means that 1.6% of the IO completed | |
608 | within 2 msecs, 16=12.8% means that 12.8% of the IO | |
609 | took more than 8 msecs, but less than (or equal to) 16 msecs. | |
71bfa161 JA |
610 | |
611 | After each client has been listed, the group statistics are printed. They | |
612 | will look like this: | |
613 | ||
614 | Run status group 0 (all jobs): | |
615 | READ: io=64MiB, aggrb=22178, minb=11355, maxb=11814, mint=2840msec, maxt=2955msec | |
616 | WRITE: io=64MiB, aggrb=1302, minb=666, maxb=669, mint=50093msec, maxt=50320msec | |
617 | ||
618 | For each data direction, it prints: | |
619 | ||
620 | io= Number of megabytes io performed. | |
621 | aggrb= Aggregate bandwidth of threads in this group. | |
622 | minb= The minimum average bandwidth a thread saw. | |
623 | maxb= The maximum average bandwidth a thread saw. | |
624 | mint= The smallest runtime of the threads in that group. | |
625 | maxt= The longest runtime of the threads in that group. | |
626 | ||
627 | And finally, the disk statistics are printed. They will look like this: | |
628 | ||
629 | Disk stats (read/write): | |
630 | sda: ios=16398/16511, merge=30/162, ticks=6853/819634, in_queue=826487, util=100.00% | |
631 | ||
632 | Each value is printed for both reads and writes, with reads first. The | |
633 | numbers denote: | |
634 | ||
635 | ios= Number of ios performed by all groups. | |
636 | merge= Number of merges io the io scheduler. | |
637 | ticks= Number of ticks we kept the disk busy. | |
638 | io_queue= Total time spent in the disk queue. | |
639 | util= The disk utilization. A value of 100% means we kept the disk | |
640 | busy constantly, 50% would be a disk idling half of the time. | |
641 | ||
642 | ||
643 | 7.0 Terse output | |
644 | ---------------- | |
645 | ||
646 | For scripted usage where you typically want to generate tables or graphs | |
6c219763 | 647 | of the results, fio can output the results in a comma separated format. |
71bfa161 JA |
648 | The format is one long line of values, such as: |
649 | ||
650 | client1,0,0,936,331,2894,0,0,0.000000,0.000000,1,170,22.115385,34.290410,16,714,84.252874%,366.500000,566.417819,3496,1237,2894,0,0,0.000000,0.000000,0,246,6.671625,21.436952,0,2534,55.465300%,1406.600000,2008.044216,0.000000%,0.431928%,1109 | |
651 | ||
652 | Split up, the format is as follows: | |
653 | ||
654 | jobname, groupid, error | |
655 | READ status: | |
656 | KiB IO, bandwidth (KiB/sec), runtime (msec) | |
657 | Submission latency: min, max, mean, deviation | |
658 | Completion latency: min, max, mean, deviation | |
6c219763 | 659 | Bw: min, max, aggregate percentage of total, mean, deviation |
71bfa161 JA |
660 | WRITE status: |
661 | KiB IO, bandwidth (KiB/sec), runtime (msec) | |
662 | Submission latency: min, max, mean, deviation | |
663 | Completion latency: min, max, mean, deviation | |
6c219763 | 664 | Bw: min, max, aggregate percentage of total, mean, deviation |
71bfa161 JA |
665 | CPU usage: user, system, context switches |
666 |